The present invention deals with a filter for removing bacterial contamination, and, a facility and treatment method for liquid waste filtration.
The standard P16-603 reference DTU 64.1 dated December 1992, published and distributed by the French Standardization Association (AFNOR), entitled xe2x80x9cImplementation of private sewage disposal equipmentxe2x80x9d, describes the implementation rules relating to private sewage disposal equipment such as domestic wastewater treatment from dwellings of one to ten principal rooms. The clauses of this standard, concern the treatment systems composed of an anaerobic pretreatment septic tank and a reconstituted in-place ground spreading system or a sand filtration system.
This standard particularly specifies that sand filters must contain washed siliceous sand which is stable in water, having a size-distribution curve which conforms to a certain grading range represented in FIG. 9.
This standard also specifies that sand filters size must not be under 5 m2 /equivalent inhabitant.
Dimensions of such sand filters remain large, which causes numerous drawbacks or constraints: large required ground surface, elevated cost, etc.
A filter is proposed for wastewater treatment, of a type which includes:
an inlet for the water to be treated;
an outlet for the treated water;
filtration equipment between the inlet and the outlet, characterized by the fact that the filtration equipment includes:
two pipe and tube systems, respectively for distribution and drainage, each located at the inlet and the outlet, placed mutually facing and spaced apart from each other, and containing perforations distributed lengthwise along their transverse walls;
filtration equipment between the two systems; distribution equipment connected with the network of distribution pipes, meant to ensure the diffusion of water to be treated toward the filtration equipment.
A water tratment septic tank is proposed which includes a barrier, a delivery pipe for wastewater, an evacuation pipe for clean water towards a spreading system, equipment for decantation of the heaviest matter at the bottom of the barrier, and of surface accumulation of grease and light particles, and of at least partial liquefaction of these materials by anaerobic fermentation, protective equipment for the spreading system to prevent plugging, integrated in the barrier, characterized by the fact that the equipment of settling, liquefaction, and protection are placed in a single compartment of the barrier; the delivery pipe forms an elbow the downward-sloping section of which leads towards an inlet end wall of the barrier and the outlet of which is opened towards the top; it includes a first deflector placed in the barrier transversely, at least approximately at outlet level, vertically inclined; a vertical partition, situated partly above and partly below the free surface S, at least approximately at the base of the lower edge of a second deflector containing an inclined lower section, is associated with an evacuation pipe; the vertical partition, the second deflector and the lateral partitions define a passage for clear water, containing an inlet which is approximately vertical, an elbow, and an outlet cover connected to the evacuation pipe.
According to the first aspect, the invention concerns a filter for removing bacterial contamination of effluents, the filtration equipment of which contains:
two systems of pipes, for distribution and drainage respectively, each one placed at the filter inlet and outlet, placed approximately facing and distanced from each other, and containing perforations distributed lengthwise in their transverse walls,
filtration equipment placed between the two systems, in the form of at least one layer of sand the size distribution curve of which is in compliance with the range defined in AFNOR DTU no. 64-1, Ref. P 16-603, able to ensure the removal of a substantial part of the bacterial contamination of the effluent passing through the filter, and
distribution equipment connected to the distribution pipes system, in order to ensure delivery of the water to be treated towards the filtration equipment.
According to other characteristics of the filter, it is between 0.2 and 0.9 m2/equivalent inhabitant in dimension.
The distribution pipes system is adjacent to the first surface of the granular filtration layer, notably located on the outside.
The drainage pipe network is next to a second surface of the granular filtration layer, notably located in a drainage layer situated below the granular filtration layer, the filtration layer and the drainage layer being separated by a synthetic drainage mat weighing around 100 g/m2.
The filter also contains a protection layer, in which is located the network of distribution pipes, and which is adjacent to the granular filtration layer.
The distribution pipes system contains at least one layer of several pipes spaced apart from each other transversely, and connected to each other especially near the inlet. The perforations in the distribution pipes system are distributed approximately perpendicular to the depth of the granular filtration layer.
The distribution pipes contain overflow openings distributed lengthwise, opposite the first surface of the granular filtration layer.
The distribution pipes are respectively covered with protective equipmentxe2x80x94such as an overturned gutterxe2x80x94meant to avoid any clogging of perforations and/or overflow openings without preventing the distribution of effluents.
One of the means of distribution is in the form of a layer for the absorption and diffusion of effluents, placed between the distribution pipes system and the filtration equipment.
One of the means of distribution is in the form of bands for the absorption and diffusion of water, placed between the distribution pipes system and the filtration equipment. These bands appear in the form of a drainage layer and a fine filtration layer, successively, in the direction of flow. The distribution pipes are placed in the median part of these bands.
The drainage system contains at least one layer of several pipes, transversely spaced in relation to each other, and connected with each other especially near the filter outlet.
The filter also contains an outer casing which houses the two systems of distribution and drainage pipes respectively, the filtration equipment between the two systems, and the distribution equipment connected to the distribution network. This casing contains an inlet and an outlet. The casing is in the shape of a U the opening of which is notably closed. Such a filter may also contain a sequential effluent injection device, such as an electric pump, a rocking bucket or a siphon primed by a pressure cover.
According to the second aspect, the invention concerns a treatment facility for domestic wastewater containing from upstream to downstream:
a septic tank for all kinds of water;
a pre-filter covered with pozzolano or an equivalent material;
the first filter containing a filtration equipment of a minimum one granular filtration layer with a porosity between around 0.2 and 5 mm, ensuring the removal of a substantial part of organic matter from the effluents; and
the second filter identical to the one described above.
According to other characteristics of the facility, the first and second filters present a similar or analogous general structure.
The first filter is between 0.2 and 0.9 m2/equivalent inhabitant in dimension. The septic tank for all waters is between 0.2 and 1 m3/equivalent per inhabitant in dimension.
The septic tank includes a barrier, a delivery pipe for liquid waste, an evacuation pipe for clear water towards the first filter, and equipment of decantation by deposit of the heaviest materials on the bottom of the barrier, and by surface accumulation of grease and light particles, and of at least partial liquefaction of these materials by anaerobic fermentation, and equipment of protection for the first and second filters, integrated in the barrier itself, to prevent their clogging.
The decantation, liquefaction, and protective equipment are located in a single compartment of the barrier. The delivery pipe forms an elbow the downhill section of which leads to the inlet edge wall of the barrier, and its outlet is opened towards the top. The septic tank contains a first deflector transversely placed in the barrier, approximately at the level of the outlet, extending over all, or most of the width of the barrier, vertically inclined at 35 to 45 degrees from the bottom to the cover, and from the inlet edge walls towards the outlet edge walls, the first deflector""s function being to improve decantation and to limit the progress of turbulence to the bottom of the barrier. To the evacuation pipe is connected a vertical partition, located partly above, partly below the free surface, approximately in line with the lower edge of the second deflector. The latter contains a lower section inclined from the bottom to the cover, and from the inlet edge walls to the outlet edge walls. The vertical partition, the second deflector, and the lateral partitions create a passage for clear water, containing an approximately vertical inlet opening, an elbow, and an outlet opening connected with the evacuation pipe.
The upper section of the septic tank""s delivery pipe is located at a higher level than the one of the evacuation pipe.
The barrier of the septic tank includes two identical or approximately similar parts: a lower shell and an upper shell, each having a trapezoidal shape in right transverse and longitudinal section, the two shells being connected to each other by their large common base.
The delivery pipe, the evacuation pipe, as well as the vertical partition and the second deflector are entirely located in the upper shell, which contains in its cover two inspection holes, while the first deflector is located at least partially in the upper shell and near the base.
The sizes of the first deflector, the second deflector and the vertical partition allows their passage through an inspection port.
The lower edge of the first deflector determines the upper acceptable level of accumulated sludge at the bottom of the barrier.
The exchange surface between the accumulated sludge at the bottom of the barrier and the floating liquid is approximately equal to all the surface of the barrier""s horizontal section at the level of the lower edge of the first deflector or of the upper surface of sludge.
In the septic tank there is a continuous and permanent free communication between the evacuation pipe and the delivery pipe for the passage of air, due to openings designated in the upper portion of the evacuation and delivery pipes.
The first deflector, the second deflector, and the vertical partition are, besides the delivery and evacuation pipes, the only parts placed on the inside of the septic tank""s barrier.
The barrier forms a single compartment, not separated in two distinct compartments by a transverse partition.
According to a third aspect, the invention concerns a domestic wastewater treatment , in which, successively:
the liquid waste to be treated is sent into an all-water septic tank;
then into a first filter which ensures removal of a substantial part of the organic matter;
then, finally, into a second filter which ensures retention of a substantial part of the bacterial contamination.
According to other characteristics, the waters leaving the second filter have:
a chemical oxygen demand less than 30 mg O2/l;
a quantity of suspended solids less than 6 mg/l;
a total quantity of KJELDAHL nitrogen less than 2 mg of nitrogen per liter;
nitrite quantities equal or close to 0;
nitrate quantities less than 60 mg of nitrogen per liter;
a quantity less than 1/ml for fecal coliforms;
a quantity less than 1/ml for fecal streptococcus.